Thermoplastic polymers combined with glass reinforcing fibers have been used in the past to produce molding compositions capable of being molded under heat and pressure to form plastic molded parts. Blends of thermoplastic polymers were often utilized in an effort to overcome deficiencies in physical properties of one or both thermoplastic polymers. The blends related to compatible or miscible polymers wherein the polymers were mutually soluble or one polymer was soluble in the other. If the two desired polymers were not miscible, then a third solubilizing polymer was added to provide solubilizing characteristics to the two desired polymers and impart compatibility to the overall polymeric mixture.
In the past, in order to obtain a smooth surface on molded plastic parts, a two-component injection molding process has been utilized wherein a second polymeric composition was injected and molded over a first fiber-reinforced polymer to achieve a smooth surface lamina. The two-component molding process, however, is difficult to control and operate in that the two separate molding compositions require controlled extruded ratios of the respective polymers, and the like.
U.S. Pat. No. 4,179,479 to Russell P. Carter, Jr. relates to novel thermoplastic polyurethane materials containing a processing aid More particularly, the patent relates to a thermoplastic polyurethane composition comprising: (A) from 40 to 100 percent by weight of a thermoplastic polyurethane, (B) from 0 to 60 percent by weight of a thermoplastic polymer selected from the group consisting of thermoplastic polycarbonates, thermoplastic polyoxymethylenes, thermoplastic acrylonitrile/butadiene/styrene graft copolymers, thermoplastic polybutylene terephthalates, thermoplastic polyethylene terephthalates, and mixtures thereof and (C) from 0.5 to 10 percent by weight based on the amount of (A) and (B), of a processing aid which is an acrylic polymer having a number average molecular weight of from 500,000 to 1,500,000.
U.S. Pat. No. 4,277,577 to Burg, et al., provides a molding composition of a mixture of an oxymethylene polymer, an elastomer having a softening temperature of below the crystallite melting point of the oxymethylene polymer and a second order transition temperature of from -120.degree. to +30.degree. C., and a segmented thermoplastic copolyester. U.S. Pat. No. 4,369,285 to Sanderson, et al., relates to reinforced thermoplastic molding compositions comprising polyamides and from 0.1 to 10 percent by weight polyurethanes.
U.S. Pat. No. 4,141,879 to Glenn G. McCarroll relates to a thermoplastic material for use under conditions demanding high strength at elevated temperatures, e.g., for under-the-hood automotive or truck components. The material is essentially a three-component alloy of a homopolymer polyamide, a copolymer polyamide, and polyurethane reinforced with a relatively small amount of glass fibers and containing normal amounts of heat stabilizers, ultraviolet screen materials, etc.
U.S. Pat. No. 4,350,799 to Hans G. Schmelzer, et al., relates to a molding composition comprising an intimate, well dispersed blend of thermoplastic polyurethane, thermoplastic polyphosphonate and thermoplastic polycarbonate which composition is characterized by an improved level of flame resistance.
Japanese Publication 61149330, dated Jul. 8, 1986, relates to an injection-molded product having a smooth surface which is prepared from a blend containing 10 parts by weight of polypropylene and 90 parts by weight of inorganic filled polypropylene. There is little, if any, significant change in physical properties.
Additionally it has been surprisingly discovered that when a modified polyethylene terephthalate (PET), as described hereinbelow, is used instead of unmodified PET, it is possible to use a lower processing temperature so as to essentially eliminate degradation of the other thermoplastic polymer during compounding or molding. Even more surprising is the unexpectedly superior improvement in the impact strength of the polymers such that the notched and unnotched Izod impact values are two times or greater for formulations incorporating modified PET (M-PET) over formulations with unmodified PET.